This application claims the priority of German Patent Application Serial No. 100 56 799.1, filed Nov. 14, 2000, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a ground support for mobile cranes, excavators and the like.
German Pat. No. DE 297 19 953 U1 describes an outrigger assembly for support of a mobile crane on the ground. The mobile crane has a frame structure oriented in the longitudinal axis of the vehicle and includes for crane operation a four-point outrigger assembly which is partially associated to the forward end of the frame structure and partially to the rearward end. Each outrigger has an outer outrigger arm and an inner outrigger arm movably disposed in the outer outrigger arm. Each outer outrigger arm is movably received in an opening of the frame structure in a direction transversely to the longitudinal axis, with two outrigger arms being supported behind one another in longitudinal axis, with two outrigger arms being supported behind one another in parallel relationship in the direction of the longitudinal frame axis. Mounted to each end of the inner outrigger arm is a support cylinder which is movable in vertical direction with respect to the ground and has free ends for attachment of a support pad. The inner and outer outrigger arms have a rectangular cross section, which is disadvantageous in connection with a buckling resistance of the outrigger assembly so that a great wall thickness must be selected in the region of the upper side, thereby adversely affecting the ineffectual own weight of the crane.
FIG. 2 shows a perspective illustration of an outrigger assembly at the aft of a ground support, with the outrigger assembly having outrigger arms 5.1, 5.2 of hollow box-shaped configuration with conventional rectangular cross section 9, as clearly shown at the visible end face of the outrigger arm 5.2 on the right-hand side of FIG. 2. The outrigger arms 5.1 may be secured to a vehicle frame 1 via a support box 30, or may also be mounted directly to the vehicle frame. When exposed to a load, the load applies a force in a direction as indicated by arrow 10 upon the frame structure 1 and consequently also upon the outrigger assembly. As the outrigger assembly buckles elastically downwards in response to the force 10, the top side 11 of, e.g., the inner outrigger arm 5.2 is exposed to pressure, whereas the bottom side 12 thereof is under tension. As a consequence of the rectangular cross section 9 of the outrigger arms 5.1, 5.2, the buckling resistance is low so that the wall thickness of the top side 11 must be accordingly reinforced. Thus, the weight of the outrigger arms 5.1, 5.2 and therefore the ineffectual own weight of the frame structure 1 becomes greater.
It would therefore be desirable and advantageous to provide an improved outrigger assembly for mobile cranes, excavators and the like, to obviate prior art shortcomings and to exhibit a better weight configuration.
According to one aspect of the present invention, an outrigger assembly for support of a mobile crane or excavator upon the ground, includes a plurality of outriggers mounted to a vehicle frame and having free ends, wherein each of the outriggers has a ground-engaging pad connected to the free ends for vertical movement in relation to the ground, wherein each of the outriggers has at least one outrigger arm unit movable with respect to the vehicle frame between an idle position suitable for travel between sites, and an operative position suitable for support on the ground, wherein the outrigger arm unit includes an outrigger arm made of a hollow profile which has a lower part of U-shaped configuration and an upper part of calotte or cap-shaped configuration.
The present invention resolves prior art problems by providing the outrigger arm by way of a two part configuration so that vehicle frame as well as the outrigger arms are elastically pushed downwards by a suspended load. As a consequence, the upper side of the outrigger arms is subjected to pressure and the bottom side of the outrigger arms is subjected to a tensile load. By providing a rounding of the upper part of the profile of the outrigger arms, the buckling resistance is enhanced so that the wall thickness can be accordingly reduced. As a result, the outrigger arm can be made lighter overall so that the ineffectual own weight is reduced.
The upper part of the profile may be half-round, half-oval or of elliptic configuration. In the event of an elliptic configuration, the smaller radius may lie in the apex. With respect to the arrangement of the support pans in the end zone of the outrigger arms, the cross section of the profile may be so provided as to have two curved sections as mirror images of one another, whereby a straight horizontal section is provided in the apex area. The horizontal section can be sized small enough to allow attachment of the support cylinder while not affecting the buckling resistance. Suitably, both curved sections are configured as arcuate segments having centers which are offset relative to the vertical axis of symmetry.
The outrigger arms may be made in one piece as profiled member or may be made of two shells which have been welded together at the confronting legs of the upper and lower parts.